Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$80.53	7.838%	$86.8419	$86.84	$86.85	$86.80
Purchase #2	$156.91	3.669%	$162.667	$162.67	$162.65	$162.70
Purchase #3	$186.42	13.658%	$211.8812	$211.88	$211.90	$211.90
Purchase #4	$28.50	3.420%	$29.4747	$29.47	$29.45	$29.50
Purchase #5	$49.76	12.871%	$56.1646	$56.16	$56.15	$56.20
Purchase #6	$243.48	12.352%	$273.5546	$273.55	$273.55	$273.60
Purchase #7	$247.34	12.513%	$278.2897	$278.29	$278.30	$278.30
7 purchase totals =	$992.94		$1,098.8737	$1,098.86	$1,098.85	$1,099.00